House electric



June 4, 1929. K. ROTTGARDT VACUUM TUBE FOR AMPLIFICATION AND OSGILLATIONGENERATION Filed Sept. 2, 1921 d v r .E R6 N W N0 1 E T VP A N Il/Patented June 4, 1929.

UNITED STATES 1,716,153 PATENT OFFICE.

KARL ROTTGARDT, OF DAIEILEBL BERLIN, GERMANY, ASSIGNOR TO WESTING- HOUSEELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYL VANIA.

VACUUM TUBE FOR AMPLIFIGATION AND OSCILLATION GENERATION.

Application filed September 2, 1921, Serial No. 497,946, and in GermanyMarch 8, 1917.

(GRANTED UNDER THE PROVISIONS} GF THE ACT OF MARCH 3, 1921, 41 STAT. L,1313.)

This invention relates to tlnee-electrode vacuum tubes and nu aparticularly to the arrangement of the electrodes within the lube.

It is an ol'iject of this invention to provide a. supporting means forthe several electrodes which will. space them more closely than hasheretofore been possible. 'llhis object oi the invention relates moreparticularly to the spacing between the cathoifle and. the grid althoughit is entirely possible, by "following the teachings of this invention,to also locate the anode close to the other electrodes.

it is a further object of this invention to arrai'i ie the grid orcontrol electrode so that he maximum i-silect oi" the field of thisleclrod-e upon the eleetrtni stream will be secured. it is well knownthat the field o'l'i a charged body is more intense near the eornersthan at other points. The invention makes use ext this principle toaccomplish this object.

Other objects ot the invention will. be

A apparent hour the :liollowing detailed desci ;ion and theillustrations on the accompanying: drawings, wherein .l igr. .l is aview, in pm'speotive, of one tl orrn o't mounting for the electrodes ina vacuum tube embodying my inveiuuion.

Fig.1. it is a similar View showing; another form, the lower portions ofthe supports "iavingg' been omitted.

21 is a similar view :torm.

l igs. 4 and 5 illustrate another form of niouilzinojl or theelectrodes, Fig. i: being a section upon the line 41- of Fig. 5 and.Fig. 5 beir a section upon the line 5-5, o t Fig. 4.

showing another cathode ill and. anode The difference of potentialbetween the anode and the cathode causes a space current to tlow. Thiscurrent is controlled by changing the potential of the grid. Iii thisgrid is close to the oathod 1., smaller clninges in the potential of thegrid will be necessary to produce the desired changes in the spacecurrent. F or this reason, it is desirable to mount the electrodes sothat the grid is as close as possible to the cathode. In l, the cathmle11, the grid 12 and the anode lilare each mounted upon a pair of e anticsupports. The supports 15 at the left in this figure and the supports 16at the right are (.zaused, by their elasticity, to move away from oneanother, they thus put a ten sion upon the electrodes ll, 12 and 13. "iihen these eleitrodes are heated and expand, this resilient action of thesi'ipports keeps the el.eetro .les from sagging, so that there is nosubstantial. change in their distance apart and no danger of theircoming into contact with one another. In order to accomplish this, thesupports must be rigidly held at their lower ends. This is done bypas-ling them througl'i a glass press 17 which is part of the material.of the evacuated tube.

In Fig. 2 a similar construction is illustrated except that the cathode21, the grid. 22 and the anode 23 are shown as ribbons instead. ofWires. In order to properly support these ribbons the resilient sumyorts25 and .26 are also of considerable Width. Their lower ends are securedin place in the same way as the lower ends of the supports 1:") and 16,illustrated in Fig. l.

l ig. 3 shows a modification in which the 33 and their supports are likethe correspoiuling parts in Fig. 2. The grid 32 in this figure stands atan angle with the plane oi? the anode and the cathode. For conveniencein illiiistration, this is shown as it it were a right angle but it isobvious that any angle is possible. It the angle between the grid 32 andthe plane of the other electrodes is near 90 degrees, the grid may besupported. by wiredilce support-s and 36, although the other electrodesare sup-- ported by rihbon-like supports, as described in connectionwith Fig. 2.

The mounting illustrated in Figs. 4 and 5 has a ring-shaped cathode ell.Preferably,

this is not a complete ring but instead is made in the form of a loopwhich nearly completes a circumference and the ends of which form theleads by which the heating current for the cathode is conducted. Theanode, in this form, consists of a conducting tube which goes throughthe plane of the ring a l. The grid i3 is in the form of a ringsurrounding the anode &5 and con tained within the ring ll. The materialof this ring-shaped grid is preferably rectangular in cross section sothat the grid ali'ords sharp edges, or corners, where its end surfacesjoin its cylindrical surface. The grid is separated from the tubularanode by a layer of insulation as: and from the ring-shaped cathode by alayer of insulation 42. The leads d6, which form the ends of thecathode, may also serve as the support for the whole system ofelectrodes, or, if desired, any other supporting means may be employed.a

The mounting illustrated in Figs. 6 and 7 also has a ring-shaped cathode51. ends of this cathode may serve as supports, as described inconnection with Fig. 5 or any other desired form of support for leadingthe heating current to this cathode, may be employed. The grid in thisform of the device is a ring 52, the radial section of which ispreferably U-shaped, so that the two flanges of the ring extend beyondthe circumference of the cathode 51, while the cylindrical part of thegrid is within the cathode. The cathode 51 and the grid 52 are separatedby insulation 53, preferably this insulation does not extend out as faras the edges of the flanges on the grid 52. The anode 5G is similar inshape to the grid. The tubular part of the anode is within the tubularpart of the grid and the flanges of the anode do not extend outward asfar as the flanges of the rid. rates the anode from the grid. 52.Preferably, this insulation does not extend to the edges of the flangeson the anode and,

even if it should do that, it ought not to extend to the edge of theflanges on the grid.

Tn the operation of the tube, the electron stream from the cathode tothe anode, must go by the grid. in the form shown in Fig. 1, the grid 12being very close to the cathode 11, enables it to have a stronginfluence upon the electron stream. In the form shown in Fig. 2, thegrid 22 extends for considerable distance parallel to the electronstream and so readily exerts a considerable influence thereon. In theform shown in Fig. 3, the grid 32. being oblique to the plane of theother electrodes, the electron stream must pass around the edges of thegrid. The charge upon the grid produces a stronger iield at the edgesthan elsewhere. The electron stream, therefore, is obliged to passthrough the strongest part of the field of The Insulation 5 L sepa- Hthe grid and so is readily influenced. In the form shown in Figs. a and5, the electron stream between the filament ll and the anode 45 isobliged to pass by the corners of the grid 43 and so is subjected to theac ion of the strongest part of the hold of the grid. In the form shownin Figs. (3 and. 7, the electron stream from the cathode 5i and theanode is obliged. to go around the edges of the flange 52 and there isacted upon by the strongest part of the field of the grid.

It has been found by experiment that tubes may be made in the waydescribed herein, so that the distance between the cathode and the gridis not more than a few tenths of a millimeter, and, with such tubes, achange in the potential of the grid amounting only to a fraction of avolt is sullicient to control the electron stream even when the platepotential is large.

The electrodes used may be wire or strips of platinum or tantahun. lVhenstrips of foil are used it is necessary that considerable care beemployed in cutting out the strips, in order that they may be mounted atthe small distance apart, illustrated in Fig. 2. ()rdinary foil may beused for all three electrodes or, if desired, the grid may beperforateC, as illustrated in Fig.

For the forms illustrated in Figs. 4- and (5, the tubular anode may bemade 01? any suitable metal, such as tantalum, platinum, nickel, copper,etc. The insulation used may be either mica or any of the usual. oxides.

Although I have illustrated a limited number of forms of supportsembodying my invention, it is obvious that many other forms will comewithin the spirit of the invention, and I, therefore, do not desire thepatent granted to be limited except as necessitated by the prior art .orindicated by the claims.

I claim as my invent-ion:

1. ln a thermionic device, an anode, a control ele :trode, a cathode andsolid insulating means separiiiting said electrodes and in intimatecontact with each, whereby relative movement of the electrodes ispositively prevented and the device is rendered nonmicrophonic.

2. A thern'iionic device including a tubular anode, a ring-shapedcathode and spoolshaped grid between them, the flanges of the gridprojecting beyond the circumference of the other electrodes.

3. in a thermionic device, three concentric ring-shaped electrodes andsolid insulation separating said electrodes, the thickness of saidinsulation. being approximately the same as the thickness of thematerial of the electrodes.

In testimony whereof I afiix my signature.

D11. KARL ROTTGARDT.

